title: Antiplatelet effects of dietary nitrate in healthy volunteers: involvement of cGMP and influence of sex.
abstract: Ingestion of vegetables rich in inorganic nitrate has emerged as an effective method, via the formation of a nitrite intermediate, for acutely elevating vascular NO levels. As such a number of beneficial effects of dietary nitrate ingestion have been demonstrated including the suggestion that platelet reactivity is reduced. In this study we investigated whether inorganic nitrate supplementation might also reduce platelet reactivity in healthy volunteers and have determined the mechanisms involved in the effects seen. We conducted two randomised crossover studies each in 24 (12 of each sex) healthy subjects assessing the acute effects of dietary nitrate (250 ml beetroot juice) or potassium nitrate capsules (KNO3, 8 mmol) vs placebo control on platelet reactivity. Inorganic nitrate ingested either from a dietary source or via supplementation raised circulating nitrate and nitrite levels in both sexes and attenuated ex vivo platelet aggregation responses to ADP and, albeit to a lesser extent, collagen but not epinephrine in male but not female volunteers. These inhibitory effects were associated with a reduced platelet P-selectin expression and elevated platelet cGMP levels. In addition, we show that nitrite reduction to NO occurs at the level of the erythrocyte and not the platelet. In summary, our results demonstrate that inorganic nitrate ingestion, whether via the diet or through supplementation, causes a modest decrease in platelet reactivity in healthy males but not females. Our studies provide strong support for further clinical trials investigating the potential of dietary nitrate as an adjunct to current antiplatelet therapies to prevent atherothrombotic complications. Moreover, our observations highlight a previously unknown sexual dimorphism in platelet reactivity to NO and intimate a greater dependence of males on the NO-soluble guanylate cyclase pathway in limiting thrombotic potential.
authors.affiliation: Centre of Clinical Pharmacology, William Harvey Research Institute, Barts NIHR Cardiovascular Biomedical Research Unit, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ.
authors.forename: Shanti
authors.initials: S
authors.lastname: Velmurugan
authors.affiliation: Centre of Clinical Pharmacology, William Harvey Research Institute, Barts NIHR Cardiovascular Biomedical Research Unit, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ.
authors.forename: Vikas
authors.initials: V
authors.lastname: Kapil
authors.affiliation: Centre of Clinical Pharmacology, William Harvey Research Institute, Barts NIHR Cardiovascular Biomedical Research Unit, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ.
authors.forename: Suborno M
authors.initials: SM
authors.lastname: Ghosh
authors.affiliation: Centre of Clinical Pharmacology, William Harvey Research Institute, Barts NIHR Cardiovascular Biomedical Research Unit, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ.
authors.forename: Sheridan
authors.initials: S
authors.lastname: Davies
authors.affiliation: Centre of Clinical Pharmacology, William Harvey Research Institute, Barts NIHR Cardiovascular Biomedical Research Unit, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ.
authors.forename: Andrew
authors.initials: A
authors.lastname: McKnight
authors.affiliation: Centre of Clinical Pharmacology, William Harvey Research Institute, Barts NIHR Cardiovascular Biomedical Research Unit, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ.
authors.forename: Zainab
authors.initials: Z
authors.lastname: Aboud
authors.affiliation: Centre of Clinical Pharmacology, William Harvey Research Institute, Barts NIHR Cardiovascular Biomedical Research Unit, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ.
authors.forename: Rayomand S
authors.initials: RS
authors.lastname: Khambata
authors.affiliation: Centre of Clinical Pharmacology, William Harvey Research Institute, Barts NIHR Cardiovascular Biomedical Research Unit, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Webb
authors.affiliation: School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK.
authors.forename: Alastair
authors.initials: A
authors.lastname: Poole
authors.affiliation: Centre of Clinical Pharmacology, William Harvey Research Institute, Barts NIHR Cardiovascular Biomedical Research Unit, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ. Electronic address: a.ahluwalia@qmul.ac.uk.
authors.forename: Amrita
authors.initials: A
authors.lastname: Ahluwalia
mesh_terms: D000293:Adolescent; D000328:Adult; D027461:Beta vulgaris; D001792:Blood Platelets / Q000378:metabolism*; D002318:Cardiovascular Diseases / Q000188:drug therapy; D003094:Collagen / Q000494:pharmacology; D018592:Cross-Over Studies; D006152:Cyclic GMP / Q000096:biosynthesis; D004032:Diet; D019587:Dietary Supplements; D004837:Epinephrine / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D006162:Guanylate Cyclase / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D009566:Nitrates / Q000008:administration & dosage / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism; D019007:P-Selectin / Q000096:biosynthesis; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D017680:Potassium Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D012737:Sex Factors; D014675:Vegetables; D055815:Young Adult
chemical_list: D009566:Nitrates; D019007:P-Selectin; D010975:Platelet Aggregation Inhibitors; D017680:Potassium Compounds; D009569:Nitric Oxide; D003094:Collagen; D006162:Guanylate Cyclase; D006152:Cyclic GMP; C023844:potassium nitrate; D004837:Epinephrine
keywords: 3-isobutyl-1-methylxanthine; BP; IBMX; Inorganic nitrate; LTA; Nitrite; PBS; PPP; PRP; Platelet; Sper-NO; blood pressure; cGMP; light transmission aggregometry; phosphate-buffered saline; platelet-poor plasma; platelet-rich plasma; spermine-NONOate.